Hinged drum system

ABSTRACT

A magnetic drum has a plurality of record-reproduce heads along its surface. A common shaft having pins at precisely spaced intervals serves both to hold the heads in registration and to lift them from the surface of the drum. The device is journaled in bearings which serve as doweling to position split-end plates of the drum housing assembly. The drum is removable to permit interchangeability.

United States Patent 1 1 Watson May 28, 1974 HINGE!) DRUM SYSTEM 3,623,120 11/1971 Lichowsky 1. 346/138 [75] Inventor: James Power Watson, Palm Beach,

Primary Examiner-Vincent P. Canney [73] Assignee: RCA Corporation, New York, NY. Attorney, g or Firm-Raymond S i y; 22 Filed: Dec. 11, 1972 ward Norton [21} Appl. N0.: 314,004

Related US. Application Data [57] ABSTRACT [62] Division of Ser. No. 202,343, Nov. 26, 1971, Pat. No.

A magnetic drum has a plurality of record-reproduce heads along its surface. A common shaft having pins [52] US. Cl 346/138, 346/74 MD at precisely paced intervals serves both to hold the [51] ll lt. Cl. Gllb 5/76 heads in registration and to lift them from the surface Fleld of Search 74 of the drum. The device is journaled in bearings which 3 7 A serve as doweling to position split-end plates of the drum housing assembly. The drum is removable to [56] References C ed permit interchangeability.

UNITED STATES PATENTS 3,174,152 3/1965 Magizy 346/74 MD 6 Claims, 6 Drawing Figures PATENTEBmza m4 '3Q813L678 sum 2 ar 4 HINGE!) DRUM SYSTEM This is a division of application Ser. No. 202,343, filed Nov. 26, I971, now US. Pat. No. 3,747,081.

BACKGROUND OF THE INVENTION In magnetic data storage units there is a need for lowcost and yet low-maintenance devices. This is particularly true of voice response units such as used by telephone companies to play prerecorded messages in response to customer calls. Previous units which generally comprise a drum and a plurality of heads each reading a track on the drum have required many adjustments to properly align the parts. This results in a high assembly cost and a high cost for field maintenance to make periodic readjustments. In addition, the drum is usually fixed in (i.e. not removable from) the unit. Therefore, when a large part of the information on a drum has to be changed, this must be done by rerecording on the machine, a costly proposition.

SUMMARY OF THE INVENTION An easily demountable drum system. It includes a number of features such as the drum housing being formed in two parts and with depressions in the end walls in which the drum bearings seat providing alignment reference between the drum and end walls. The heads all may be lifted from the drum surface concurrently. Means are provided for self-aligning the head assemblies and for normally causing them to engage the drum surface. These and a number of other features are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a drawing, partially in section of a magnetic data storage unit which includes the present invention;

DETAILED DESCRIPTION In FIG. I a magnetic data drum assembly and drive unit 12 are each attached to a common base plate 14. The drive unit may comprise any suitable driving means such as a motor 16 shown largely hidden behind gear reduction unit 18. Output shaft 20 of gear reduction unit 18 is coupled through a coupling 22 to drive a drum unit 24, only the lower portion of which is visible in FIG. 1.

The drum has on its surface a magnetic recording material on which data of either digital or analog type may be written along a plurality of tracks, each track extending circumferentially about the drum. For example. information may be recorded on 64 parallel tracks on drum unit 24.

Each track may have associated with it a recordreproduce head assembly. Twenty-two such head assemblies identified by the numeral 26 followed by a numeral to uniquely identify each head (i.e. 26-ll through 26-22) are illustrated. As will be seen in connection 2 with other figures, there may be two other sets of 2] head assemblies numbered 26-23 through 26-43 and 26-44 through 26-64 spaced at other positions about the surface of the drum, thus bringing to 64 the total of such head assemblies. With such an arrangement, therefore, head assemblies 26-1 and 26-2 may be spaced a distance apart equal to three tracks. The other head assembly groups are then also spaced apart a distance equal to three tracks so they will fill in the spaces between heads 26-l and 26-2, etc.

The 22 head assemblies 26 shown in FIG. 1 rest on a common shaft 28a. (There are also two other shafts 28b and 28c, one for each other group of head assemblies shown in FIG. 3.) Shaft 28a, which will be described in more detail later, acts, in conjunction with other elements to be described to accurately position the heads with respect to the drum 24. The shaft extends between side plates 30 and 32 (the side plates are split into upper and lower parts receiving the designations 0 and b respectively) and is held in precise registration relative to side plate 32. by means of C washer 34 to the left of the guide plate and spring washer 36 to the right of the guide plate. The spring washer acts to hold C washer 34 in contact against side plate 32 and therefore provide accurate registration of shaft 28a and heads 26 relative to the side plate.

Drum 24 is lubricated by a lubricating assembly 38 comprising a pan 40 filled with a suitable lubricant and a wick 42 which resides in pan 40 and has an end which is at all times in contact with the surface of drum 24. A cover 41 (shown broken away) covers the entire drum assembly 10 to prevent contaminants from being attracted to the drum 24.

An assembly generally labeled 37 is attached to the three shafts 28 a, b and c for the purpose of lifting heads 26 from the surface of drum 24. Assembly 37, shown in greater detail in FIG. 2, comprises three partial pulleys 50-l, 50-2 and 50-3, and the various components attached thereto. Each of the pulleys is attached to its shafts 28 a, b and c by a fastener 64 a, b or c, respectively. A cable 52 secured to pulley 50-! by fastener 53 extends over pulleys 50-2 and 50-3 and terminates at a lever 54. The pulleys are also attached to one end of tension springs 56 a, b and c respectively. The other ends of the springs are attached to the side plate 32. Finally, the pulleys are attached to second tension springs 58 a, b and c respectively and these springs are secured at their other end to cable 52. Stop pins 60 a, b and 0, attached to side plate 32, reside in slots 62 a, b and c respectively, in the different pulleys and thereby limit the travel of the pulleys.

Lever 54 (illustrated in its halfway point) pivots about screw 66 between two extreme positions. The first is when it has traveled counter-clockwise to a position such that pin 68 which is attached to plate 32 resides in slot 70 (shown in phantom). The second is when it has traveled clockwise to a position in which the pin 68 resides in slot 72 (shown in phantom). The length of cable 52 is designed such that when lever 54- is in its full counter-clockwise position, the cable is slack and all pulleys 50 are in their full counterclockwise position limited by pins 60 a, b and c. The pulleys are moved to and held in this counter-clockwise position by springs 56 a, b and c. When lever 54 is rotated to its full clockwise position, tension is applied to cable 52. Since the cable passes over each of pulleys 50, it tends to rotate them in the clockwise direction.

Springs 58 a, b and c attached to the pulleys take up any uneven tension from one pulley to another so that all pulleys are rotated to their full clockwise position.

The purpose of the arrangement just described is to lift each of head assemblies 26 from contact with drum 24 as will better be seen in FIG. 3, to which the readers attention is now directed. In FIG. 3 which is a crosssection taken along lines 3-3 of FIG. I, head assemblies are shown in greater detail. In FIG. 3 three head assemblies are shown numbered 26-22, 26-43 and 26-64 respectively. Each of the head assemblies shown is one of a plurality of head assemblies extending back (into the drawing) from the three head assemblies shown. Each of the head assemblies is attached to a shaft 28 which is made of centerless ground stock. Each shaft 28 has two parallel flat portions 71 ground on it. Flats 71 are spaced apart a distance less than the width of slot 73 in the head assemblies, thus permitting removal of the head assemblies in a manner to be described shortly.

A pair of wires 74 lead from each head assembly to pin and socket connectors 76 in a cable harness assembly 80. One pin 77 is removed from socket 79 to show the ease with which electrical connections are made. Cables 80 (there is one for each of the three head assemblies) exit from the left side (as illustrated in FIG. I) of drum assembly 10. The cable assemblies reside in U-shaped cable channels 81 which extend between side plates 30 and 32 being attached thereto by fasteners 35 (see FIG. I) to permit easy removal after all pins 77 have been removed from sockets 79. From the cable harness assembly 80, wires (not shown) lead to a switching assembly which in turn may be connected to any suitable load or amplifying means. The switching assembly is not shown. It may be of any conventional design and its purpose is to permit one of the heads at a time to be selectively coupled to the amplifying means (also not shown) or other load. A third unused socket 79 in assembly 80 may be coupled to a noise shield (not shown) which may be placed between adjacent head assemblies. This socket 79 may be grounded or connected to some other suitable noise suppressing circuitry.

Drum 24 shown in better detail in FIG. 3 comprises a solid metal cylinder 83 surrounded by a magnetic elastomer 82 on which the magnetic tracks of information are recorded.

Lubrication assembly 38 is also shown in greater detail than in FIG. 1 and in the section partially broken away shows a compression spring 90 urging the vertical portion (as illustrated) of felt wick 42 against the drum surface 82. Spring clip 92 serves as both a handle to remove tray 40 to which it is attached from the drum assembly and to hold the tray in the position shown by means of dimple 94 in base 14.

In FIG. 4 which illustrates one head assembly 26 in greater detail, the head is shown removed from bar 28b. A portion 102 of head 26 is broken away to show the earpiece 104. A similar piece 104 would be part of the area which is broken away. The two areas form a slot extending in a direction normal to the axis of shaft 28 which surrounds a projecting member such as a pin 106 in bar 28. There is one pin 106 for each of the 64 heads 26. Pin I06 serves to provide lateral positioning of this end of the head. Also when head 26 is in the position shown in FIG. 3 (i.e. so that the pole face portion 108 is in contact with drum 24) pin 106 may be used to raise the head 26 from the drum. This is done by the mechanism of FIG. 2 which by rotating the three shafts 28 rotates the pins 106 with them until the pins engage the walls 110 defining the closed ends of the slots formed by earpieces 104, and raise the heads. It is desirable to raise the heads 26 from the drum when the drum is not rotating to prevent flat spots on elastomer 82 caused by pole pieces 108 and to eliminate head-drum friction during drum startup.

The end 144 of each head 26 opposite the end containing slot 72 resides in a slot in slotted bar 112. There are three such bars 112 a, b and c respectively. The bars 112, one of which is best seen in FIG. 1, run the width of drum assembly 10, extending from side plate 30 to side plate 32 and contain a slot for each head 26. Bars 112 and plates 30 and 32 are rigidly secured together to form a portion of the frame. The slots extend in a direction normal to the axis of rotation of drum 24. Sidewall portions 114 (FIG. 4) of slotted bar 112 position heads 26 axially with respect to the drum and also ensure that pole face 108 is kept parallel with magnetic elastomer 82 on drum 24. Another important feature of the apparatus is that the rotational center 29 of each shaft 28 is tangent to drum surface 82 at the point of contact with pole face 108. With the shaft so located heads 26 are restrained against the frictional drag of drum surface 82 and there is no tendency for pole face 108 to either bounce off the drum surface or to dig in.

Cartridge (one for each of the 64 heads 26) residing in bore 122 of bar 112, holds head 26 in contact with drum 24 (FIG. 3). Cartridge 120 is seen in FIG. 5 to comprise an outer threaded portion containing a bore 132. A portion 134 of bore 132 is threaded to receive an adjusting screw 136. A compression spring 138 also resides in the bore and extends from adjusting screw 136 to pin 140. The assembly here shown is in normal operating position with spring 138 compressed to provide maximum allowable force on pin 142. Distance 200 is sufficient to compensate for machine tolerances and also allow for pole face wear-out without bottoming" in casing bore 132.

The nose 142 of pin is in contact with toe 144 of head 26 (see FIG. 4) and acts to urge the head against drum 24. Screw 136 is adjusted to provide the desired pressure to head 26 and is the only adjustment of significance on the entire drum unit. Spring 138 may be made of sufficient length so that essentially constant pressure is maintained even though pole face 108 of head 26 (see FIG. 4) wears. Therefore, no field adjustment of screw 136 is required and in fact in production the screw may be fixed so that it cannot be turned at the field sites. The pressure exerted by spring 138 is sufficiently light to allow the heads 26 to be raised off of the drum when the mechanism of FIG. 2 turns shafts 28 a, b and c.

Returning again to FIG. 4, cartridge 120 is shown removed from its normal position to permit removal of head 26. A ledge 149 at an end of member 151 prevents cartridge 120 from being removed completely from bar 112 and in this way prevents it from being misplaced or dropped onto moving drum 24. Member 151 is secured to bar 112 by screws 202 (one of two shown). Merely loosening these screws allows ledge portion 149 to be tipped back sufficiently to permit removal of any or all of cartridges 120 for adjustment or replacement.

In FIG. 6 drum assembly 10 is illustrated in its open position with drum 24 removed. The drum 24 is removable to permit replacement for any reason such as if the drum becomes damaged or if it is desired to substitute a drum containing new information. Drum 24 rotates about a shaft 150 extending through the drum and protruding at both ends. On each end of shaft 150 is a bearing means such as an oilite or low-friction plastic, one-piece element or, as shown, a ball bearing 152, (ball bearing 152 on the left end of shaft 150 as illustrated in FIG. 6 is hidden by the drum). Ball bearings 152 in addition to providing the usual low-friction interface between shaft 150 and opposing side plates 30 and 32 also act as dowel members.

The doweling works as follows. Bearings 152 reside in tight-fitting bores 160 in each of side plates 30 and 32. The roller bearings are the only means of aligning side plates 30a and 32a relative to side plates 30b and 326. This is so because screws 162 which hold the upper side plates to the lower side plates reside in oversized openings in the upper side plates. Further, as best seen in FIG. 2, the hinging mechanism for the upper side plates includes a screw 164 (for each side plate) which holds in place pins 166 about which the upper side plates pivot. As seen in FIG. 2, the screw E64 is loosely fitted through bore in lower side plate to allow lateral movement between upper and lower side plates. It is heavily spring loaded to secure this end of the side plates in tight frictional relationship after they have been doweled into position by the bearings during closing. The other end of side plates are secured in similar relationship by screws 162. Therefore, the only method of positioning the upper side plates relative to the lower side plates is via ball bearings 152.

The final result is that the upper and lower side plates are positioned accurately relative to drum 24 and since the various head assemblies are positioned accurately relative to the side plates they are therefore automatically positioned accurately relative to the drum 24.

To summarize there has been described a drum memory assembly containing a number of unique features, perhaps the most important of which is that with the exception of one factory-set adjustment of spring pressure in cartridge 120, there is not a single adjusting device in the entire assembly. The result is inexpensive assembly cost and low field maintenance cost. Also since the drum end plates 30 and 32 are split, the drum '24 may be easily removed for replacement.

Heads replacement with no degradation of signal and no adjustments required (or provided) is made possible because of the precise alignment provided both ends of the head.

Accurate positioning of one end of heads 26 is assured. Since it is an easy matter to accurately position head aligning pins 106 along shaft 28, an inexpensive centerless ground stock, having tight tolerances, and since the end of each shaft 28 a, h, c is held solidly against end plate 32 by wavey washers 36. The other end of heads 26 are accurately positioned, because elements 112 containing a close tolerance slot for each head are also rigidly attached to end plates 30 and 32.

Accurate alignment is not achieved at the expense of easy head removal. Head'removal is accomplished simply by loosening cartridge 120 against stop 149 positioned to prevent the screw being fully removed and therefore possibly lost. The head is then simply rotated about shaft 28 until slot 72 lines up with flat portions on the shaft whereupon the head can easily be slipped off of the shaft as best seen in FIG. 4. Electrical disconnection of the head is easily accomplished by removing pins 76 from sockets 77 (FIG. 3).

Cable assembly 80 is easily removed from the apparatus (should this become necessary) by removing two screws 35 (FlG. l) permitting the removal of cable channel 81 containing cable 80.

A head lifting mechanism 37 provides for the easy lifting of all 64 heads 26 from the surface 82 of drum 24 by the simple expedient of rotating lever 54 (FIG. 2). As the lever is rotated, shafts 28 and pins 106, which also serve to axially align the heads, are also rotated causing the heads to be lifted.

Finally a lubricating assembly 38 contains a felt wick 42 which ensures lubrication of drum 24 while metal container 40 containing the lubricant being slidably attached to side plates 30 and 32 cannot come in contact with drum 24 causing possible damage.

What is claimed is:

1. An easily demountable drum system comprising, in combination:

a hollow drum housing having two end walls, an axis about which the drum is to rotate passing through the end walls, and a third wall joining the end walls, said housing being formed of two parts which are movable relative to one another and which meet at said third wall along lines parallel to said axis, the end walls of said housing each being formed with a depression at the inner surface thereof, symmetrical about said axis and extending into both parts of said housing, each depression shaped to receive a bearing housing;

a drum located in said drum housing, said drum having end walls through which said axis passes and shaft means extending from said drum end walls located on said axis; and

a pair of bearing means each rotatably attached to an opposite end portion of said shaft means and each located in one of said depressions, whereby said drum and its bearings readily may be removed by moving the two parts of the housing apart.

2. An easily demountable drum system comprising, in

combination:

a hollow, drum housing having end walls, an axis about which the drum is to rotate passing through the end walls, and a third wall joining the end walls, said housing being formed of two parts hingedly joined to one another at said third wall along a line parallel to said axis, the end walls of said housing each being formed with a depression at the inner surface thereof, symmetrical about said axis and extending into both parts of said housing, each depression shaped to receive a bearing housing;

a drum having a center shaft on said axis and located in said drum housing; and

a pair of bearings, each fixed at its inner race to an opposite end portion of said shaft and each having an outer race housing located in one of said depressions, whereby said drum and its bearings readily may be removed by swinging open said housing at the hinged connection between the two parts of the housing.

3. A drum system as set forth in claim 2, further including:

a plurality of heads mounted in said housing and normally engaged with the drum surface; and

means coupled to all heads for concurrently moving them away from the drum surface.

4. ln combination:

drum means;

at least a bearing means coupled to said drum means for permitting rotation thereof;

two plates formed with mating edges, each plate formed with a depression in its surface at its mating edge and the two depressions together corresponding in size and shape to a portion of said bearing means; and

means securing said two plates together with the mating edges engaged and with the bearing means in place in said two depressions thereby positioning said two plates with respect to each other.

5. In the combination as set forth in claim 4, said securing means comprising a hinge at one end of the two mating edges and fastening means at the other end of the two mating edges.

6. In the combination as set forth in claim 4, one of said bearing means being coupled to each end of said drum and wherein said two plates, in which one of said bearing means resides, form one end wall of a two-part drum housing and further including two additional similar plates, in which the other of said bearing means resides, and which forms the other end wall of the drum housing. 

1. An easily demountable drum system comprising, in combination: a hollow drum housing having two end walls, an axis about which the drum is to rotate passing through the end walls, and a third wall joining the end walls, said housing being formed of two parts which are movable relative to one another and which meet at said third wall along lines parallel to said axis, the end walls of said housing each being formed with a depression at the inner surface thereof, symmetrical about said axis and extending into both parts of said housing, each depression shaped to receive a bearing housing; a drum located in said Drum housing, said drum having end walls through which said axis passes and shaft means extending from said drum end walls located on said axis; and a pair of bearing means each rotatably attached to an opposite end portion of said shaft means and each located in one of said depressions, whereby said drum and its bearings readily may be removed by moving the two parts of the housing apart.
 2. An easily demountable drum system comprising, in combination: a hollow, drum housing having end walls, an axis about which the drum is to rotate passing through the end walls, and a third wall joining the end walls, said housing being formed of two parts hingedly joined to one another at said third wall along a line parallel to said axis, the end walls of said housing each being formed with a depression at the inner surface thereof, symmetrical about said axis and extending into both parts of said housing, each depression shaped to receive a bearing housing; a drum having a center shaft on said axis and located in said drum housing; and a pair of bearings, each fixed at its inner race to an opposite end portion of said shaft and each having an outer race housing located in one of said depressions, whereby said drum and its bearings readily may be removed by swinging open said housing at the hinged connection between the two parts of the housing.
 3. A drum system as set forth in claim 2, further including: a plurality of heads mounted in said housing and normally engaged with the drum surface; and means coupled to all heads for concurrently moving them away from the drum surface.
 4. In combination: drum means; at least a bearing means coupled to said drum means for permitting rotation thereof; two plates formed with mating edges, each plate formed with a depression in its surface at its mating edge and the two depressions together corresponding in size and shape to a portion of said bearing means; and means securing said two plates together with the mating edges engaged and with the bearing means in place in said two depressions thereby positioning said two plates with respect to each other.
 5. In the combination as set forth in claim 4, said securing means comprising a hinge at one end of the two mating edges and fastening means at the other end of the two mating edges.
 6. In the combination as set forth in claim 4, one of said bearing means being coupled to each end of said drum and wherein said two plates, in which one of said bearing means resides, form one end wall of a two-part drum housing and further including two additional similar plates, in which the other of said bearing means resides, and which forms the other end wall of the drum housing. 